This disclosure relates to fluid filters including their construction and use. In particular, this disclosure concerns liquid filters to clean contaminants from fluid systems such as engine and transmission lubrication systems, engine fuel systems, and hydraulic systems.
Certain types of fluid filters, for example oil or lube filters, fuel filters, or hydraulic fluid filters, operate to remove substantial amounts of particulate material from liquid flow, typically in a circulating environment.
Such filters generally include a filter element within a drawn, relatively thin, cylindrical metal housing and a stamped metal baffle or cover plate at the open end of the housing. Typically, there is a gasket retainer projection welded to the cover plate, and the gasket retainer is secured to the housing by a roll or lock seam. A central threaded opening is provided in the cover plate for spinning the filter onto a threaded stud of a mounting base or filter head.
Fluid filters of this type can be mathematically modeled to approximate pressure vessel systems. A typical pressure vessel system is mainly subject to two types of stressesxe2x80x94hoop stress and longitudinal stress. Hoop stress is calculated by multiplying the internal pressure times the radius and dividing that product by the wall thickness of the vessel. The hoop stress acts tangent to the surface of the pressure vessel. The longitudinal stress is the stress produced at right angles to the hoop stress (i.e., parallel to the longitudinal axis of the pressure vessel.) The longitudinal stress is calculated by multiplying the internal pressure times the radius and dividing that product by two times the wall thickness.
The longitudinal stress is one-half of the value of the hoop stress. In theoretically exact pressure vessel systems, when the pressure in the pressure vessel is raised to the bursting point, failure should occur along a longitudinal seam of the pressure vessel. In other words, this means that the system is optimized for burst strength if the failure point occurs at the longitudinal stress point. If, under a burst test, the system fails at some point other than along a longitudinal seam, this means that, theoretically, the system has not been optimized for strength.
In previous existing filters having a rolled lock joint connection between the gasket retainer and the housing, as pressure is increased to the point of mechanical failure, the failure typically occurs at the rolled lock joint. This failure point is often at pressures lower than the pressure point at which the pressure vessel should fail along a longitudinal seam.
In addition, in previous existing filters having a rolled lock joint connection between the gasket retainer and the housing, there are other problems as well. As discussed above, the baffle plate or cover is typically connected to the gasket retainer with projection welds. Sometimes, the projection welds can break due to vibration or pressure pulses. When the projection welds break, the filter cannot be spun off from the filter head.
Improvements in these types of filter systems are desirable.
In one aspect, the disclosure describes a liquid filter construction including a cover plate or baffle plate attached to a can with a filter element operably oriented within an interior of the can. The baffle plate, in preferred constructions, will be metal, preferably steel, with an average cross-sectional thickness of at least about 0.080 inch (about 2 mm). In preferred constructions, the can will be metal, preferably steel, and will have an average cross-sectional wall thickness that is different from the thickness of the baffle plate, and is at least about 0.008 inch (about 0.2 mm). In certain arrangements, the baffle plate will be at least 200% of the thickness of the can. Preferably, the can will be secured to the baffle plate along a laser welded seam.
In preferred constructions, the filter element will include at least a first end cap and a media pack secured to the first end cap. The first end cap will radially abut an outer, annular surface of a tubular member forming either the inlet or outlet to formal a radially directed seal between the first end cap and the tubular member.
Filtration systems are disclosed that utilize liquid filter constructions as characterized herein. Filtration systems may comprise lubrication systems, fuel systems, or hydraulic systems. Such systems typically operate at pressures of no greater than about 200 psi (about 1.4 MPa) for lubrication systems and fuel systems. Hydraulic systems may be higher.
Methods for filtering liquid are disclosed and preferably utilize constructions and systems as characterized herein.
Methods of constructing a filter are also disclosed. Preferred methods will include laser welding a can to a baffle plate, wherein the can and baffle plate have dissimilar thicknesses.